Version 2 update: Now includes all variants (heavy/sturdy), both synth helmet versions (normal and field) and I redid the zip file so it will work with Nexus Mod Manager.

A simple retexture of synth armor to make it black.

Make sure you've edited your ini file to include the \textures directory and then simply extract to Fallout4\Data\

Shown with BoS officer uniform in the screenshot.  Also shown is mm137's great black and white Pipboy retexture.

Added image to show just the armor pieces with nothing underneath.